The Republic P-43 Lancer was a single-engine, all-metal, low-wing monoplane fighter aircraft built by Republic, first delivered to the United States Army Air Corps in 1940. A proposed development was the P-44 Rocket. While not a particularly outstanding fighter, the P-43A had a very good high-altitude performance coupled with an effective oxygen system. Fast and well-armed with excellent long-range capabilities, until the arrival of the Lockheed P-38 Lightning, the Lancer was the only American fighter capable of catching a Japanese Mitsubishi Ki-46 "Dinah" reconnaissance plane at the speeds and heights at which they flew. In addition, the P-43 flew many long-range, high-altitude photo recon missions until replaced by F-4/F-5 Lightnings (P-38 variants) in both the USAAF and RAAF.
The USAAC considered the P-43 and its variants obsolete from the start and used them only for training purposes. In fall 1942, all surviving USAAF (transitioned from USAAC in June 1941) P-43s were redesignated RP-43, indicating they were unfit for combat.[citation needed] Most of the aircraft that were not sent to China were modified for photo-reconnaissance duties and used for training. Eight P-43s (four P-43A-1s and four P-43Ds) were loaned to the Royal Australian Air Force in 1942 and served with No. 1 Photo Reconnaissance Unit. The RAAF flew many long range, high-altitude photo reconnaissance missions before the six survivors were returned to the USAAF in 1943.